Conventionally, for illuminating a room or the like, a lamp is connected to the electric mains through a switch, to be operated by a user. When a user enters a room, he switches on the light, and when he leaves the room, he switches off the light. If a room has multiple lights, the room typically has multiple switches, each switch servicing one or more lamps.
Instead of user-operable switches, also automatic switches exist, which have a built-in detector, and which switch ON or OFF depending on a detected event. For instance, light detectors switch ON automatically when it starts getting dark, and switch OFF when it starts getting lighter again. Movement detectors switch ON automatically when a movement is detected, and switch OFF when no movement has been detected for a predefined time period.
Such switches, be it user-operable or automatic, switch the mains power. Such switch can be integrated with a lamp fitting or lamp housing, or even with a light bulb itself, in which case a switch is a dedicated switch for switching one specific lamp. Such switch can also be a separate device having a switched power output, to which one or more remote lamps can be connected. In that case it is possible to detect movement in one location and switch ON the light at a distance. A disadvantage is, however, that separate power lines must be arranged from the switch to the corresponding lamps.
In the following, the word “lamp” will be used for the actual light-generating element, such as a light bulb, a fluorescent tube, etc. A lamp will be mounted in a fitting, which is arranged in a housing, possibly comprising a ballast, the housing further in general being provided with mounting means for mounting against a wall or in a ceiling; such combination will in the following be indicated by the word “luminaire”.
More recently, a system has been developed comprising multiple luminaires and a communication bus to which all luminaires are connected. One luminaire comprises an integrated movement sensor; this luminaire will be indicated as a MASTER luminaires The other luminaires do not have such sensor; these luminaires will be indicated as a SLAVE luminaire. All luminaires are connected directly to the mains. Each luminaire comprises a controllable switch, controlled by a controller that is coupled to the communication bus. The controller of the MASTER luminaire is also coupled to the integrated movement sensor. If the sensor detects a movement, the MASTER controller controls its own switch to go ON, but it also sends a digital command signal over the communication bus to the SLAVE luminaires. A SLAVE controller controls its corresponding switch in response to commands received from the MASTER controller over the communication bus. Thus, it is possible to illuminate a relatively large area (for instance an entire room) in response to detection of movement in one small region (for instance the entrance door).
In some situations, it may be that the detection zone of the movement sensor is too limited, so that it is desirable to enlarge the detection zone. For example, a room may have two or more entrances. For such situation, it would be possible to arrange a second MASTER luminaire for defining a second detection zone. A problem then would be that two (or more) masters are connected to one and the same bus, and their respective command signals may collide with each other. In order to prevent this, multi-master systems usually use a complicated communication protocol.
Another practical problem may be that no mains power line is available at the location where it is desired to add a detection zone. For such situation, it would be desirable to have available a separate, auxiliary movement detector which can be battery-powered. In order to provide long battery life, the energy consumption should be kept to a minimum. On the other hand, the auxiliary movement detector should be operational 24 hours each day.
The present invention aims to solve the above problems.